The map shows the morning low temperatures on November 24, 2010.
Note the temperature of -18 F in Wyoming, -21 F in Montana and -33 F in southern Alberta.
Mild temperatures have been the norm this Autumn across the Great Plains with 80 F and 70 F temperatures earlier during the month of November. The cold air has been bottled up in Southern Canada due to the primary jet stream being located further north than normal and blocking the southward movement of this cold air. As a result, the temperatures have continued to plunge in southern Canada reaching levels normally only seen in mid Winter. Some of this bitterly cold air has begun to spill southward into the northern Plains. Ironically, the temperatures remain summer-like in the upper 80's in southern Texas. The temperature range across the Plains is over 110 degrees.
This pattern of an extreme cold airmass across southern Canada and extreme warm airmass across the deep south is typical of La Nina winters. Nebraska, being right in the middle should experience constant contrasts as these two opposing airmasses battle for supremacy this coming winter.